The present invention relates to a radar system, and relates specifically to scanning radar systems that are particularly, but not exclusively, suitable for detecting and monitoring ground-based targets.
Radar systems are used to detect the presence of objects and to measure the location and movement of objects. In general, radar systems are designed for a specific application: to measure distance over a specified range of distances; over a specified scan region; within a specified level of accuracy; and in relation to a specified orientation. For radar systems that are required to scan over large distances, the antennas are required to generate powerful electromagnetic radiation, requiring the use of a correspondingly powerful source and specific types of antennas.
It is common for such radar systems to sweep across a given region, scanning the region for the presence of such objects. In order to sweep over the region the radar systems either employ mechanical devices comprising an antenna that physically moves in space, or electronic devices comprising elements that are arranged to steer radiation as it is transmitted or received. A problem with the mechanical radar systems is that their operation is reliant on physical components and associated control and moving parts. This inventory of parts is costly and can require a commensurately large power source.
One known group of electronic devices is phased antenna arrays, which apply various phase shifts to signals, thereby effectively steering the received and transmitted beams. These electronic devices are commonly used in RF sensor and communications systems because they do not involve physical motion of the antenna and are capable of moving a beam rapidly from one position to the next. Whilst radar systems incorporating such devices can provide an extremely accurate measure of the position of targets, a problem with these types of electronic devices is that adequate control of the beam requires often several arrays of electronics components; this increases the physical size, complexity and cost of the radar system.
Another group of such electronic devices is frequency scanning arrays, which, in response to input signals of varying frequencies, can steer a beam in an angular plane. Frequency scanning arrays have been combined with moving parts that rotate in another plane, as described in U.S. Pat. No. 4,868,574. However, a problem with this combination is that it incurs the size and cost shortcomings of regular mechanical scanning system and performance-wise, is less accurate than the phased antenna systems.
It will therefore be appreciated that the various known radar systems are one or several of costly, bulky and heavy, which limits their applicability to uses in which either cost or weight or size are an issue.